Phosphorus containing compounds for reducing acetaldehyde in polyesters polymers

ABSTRACT

Polyesters whose polycondensation is catalyzed by titanium-containing catalysts and which are susceptible to acetaldehyde formation during polycondensation or subsequent molding operations are prepared with low finished acetaldehyde content and reduced acetaldehyde generation by adding an ammonium or amine salt of an oxyphosphorus-acid. Polyesters, especially polyethylene terephthalate, may be produced with high inherent viscosity in reduced processing time, without the necessity of further polymerization in the solid state.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/229,367 filed on Sep. 16, 2005, the disclosure of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention pertains to a process for reducing acetaldehydeformation in polyesters susceptible to the formation of acetaldehyde,i.e., those containing —OCH₂CH₂O— in a repeat unit and in particular topolyethylene terephthalate (“PET”) and to PET prepared thereby.Polyesters can be prepared by melt polycondensation, with or withoutsubsequent solid state polymerization.

BACKGROUND ART

Polyethylene terephthalate (“PET”) is used extensively in packagingapplications, in particular as beverage containers. In theseapplications, it is important that the PET have a relatively highmolecular weight, generally expressed as inherent viscosity (“IhV”) orintrinsic viscosity (“It.V.”), and low amounts of acetaldehyde.

There are two types of acetaldehyde (AA) to be concerned about. Thefirst is residual or free AA contained in the pellets or particles sentto preform molders. The second type of AA is preform AA or the AAgenerated when the PET pellets are melt processed to make bottlepreforms. AA precursors in the pellets can be converted to AA uponmelting and give unacceptable levels of AA in the preforms. Meltprocessing also forms more AA precursors, which can liberate AA.Acetaldehyde has a noticeable taste and can be detected by human tastebuds at low levels. When the preforms are blown into bottles,unacceptably high AA levels are those that adversely impact the taste ofthe beverage contained in the said bottles.

Relatively tasteless beverages such as water are particularly negativelyimpacted by the strong taste of AA. Many water bottle applicationsrequire lower levels of perform AA than carbonated soft drink (“CSD”)bottle applications. Converters who take polyester particles and makebottle preforms would like to have one resin that could be used to makepreforms for both water and CSD applications. This would simplify thematerials handling process at the converter by allowing for one feedsilo or one type of feed silo, one product storage area or one type ofproduct storage area etc. Most resins sold into water bottle marketshave a lower It.V. than those resins sold into CSD markets. A dual useresin would have to a high enough It.V. for CSD applications and a lowenough AA generation rate upon melting for water bottle applications.

In order to use one resin, some converters are adding AA scavengers toCSD resins to get acceptable perform AA for the water market. AAscavengers add significant cost to the container and often negativelyimpact the color of the container by making it either more yellow ordarker as compared to an analogous container without AA scavenger added.

The conventional PET production process begins with esterification ofpredominantly terephthalic acid and ethylene glycol, or ester exchangeof predominantly dimethyl terephthalate and ethylene glycol. Theesterification need not be catalyzed. Typical ester exchange catalysts,which may be used separately or in combination, include titaniumalkoxides, tin (II) or (IV) esters, zinc, manganese or magnesiumacetates or benzoates and/or other such catalyst materials that are wellknown to those skilled in the art. The resulting mixture is thensubjected to polycondensation in the melt at elevated temperature, forexample 285° C., in the presence of a suitable catalyst. Compounds ofSn, Sb, Ge, Ti, or others have been used as polycondensation catalysts.

Following melt phase polycondensation, which generally achieves aninherent viscosity in the range of 0.5 to 0.65, the polyester isextruded, cooled, and cut into granules, which are then subjected to acrystallization process wherein at least the exterior of the granulesbecomes crystalline. This crystallinity is necessary to preventsintering and agglomeration in a subsequent solid state polymerization.Crystallization and annealing take place in a fluidized bed attemperatures of, for example 160-220° C., for several hours, asdiscussed by WO 02/18472 A2, and U.S. Pat. Nos. 4,161,571; 5,090,134;5,114,570; and 5,410,984.

Solid state polymerization or “solid stating” takes place in a fluidizedbed over a period of from 10 to 20 hours, at a temperature which ispreferably in the range of 180° C. to a temperature which is lower thanthe crystalline melt temperature by at least 10° C. Volatiles areremoved in vacuo or by a flow of inert gas (e.g., nitrogen), or at lowertemperatures, e.g. 180° C. or lower, by means of a flow of air. Avariation in this process is disclosed in U.S. Pat. No. 5,393,871 wherenitrogen containing water vapor is flowed through the solid stater.

Solid stating has the advantage that relatively high inherentviscosities can be achieved. It has the further advantage thatacetaldehyde content of the polymer is lowered substantially by theremoval of acetaldehyde by volatilization. Solid stating has theconsiderable disadvantages of high energy usage and long processingtime. Finally, solid state polymerization causes the pellets to developshell-to-core molecular weight gradients, which results in a loss ininherent viscosity during the molding of articles that is theorized tobe due to re-equilibration in the melt.

It would be desirable to eliminate solid stating, but to do so wouldrequire more extended melt-phase polycondensation. In the absence ofsolid stating, removal of acetaldehyde present at the end of the meltphase polycondensation needs to be addressed. The situation is furthercomplicated by the presence of acetaldehyde precursors which may latergenerate acetaldehyde, i.e., during injection molding of PET bottlepreforms. Without solid stating, acetaldehyde precursors may remain atthe concentration present after the melt-phase polycondensation.

When antimony catalysts are used for polycondensation, phosphorouscompounds have been added to assist in lowering acetaldehyde andacetaldehyde precursors. However, antimony is not the most activecatalyst, and deactivation of antimony with phosphorus compounds, if notperformed carefully, may generate haze in the product. Titaniumcompounds are known to be much more active polycondensation catalysts,and can reduce the polycondensation time significantly. However,titanium compounds, when employed in PET production, often producepolymers with higher residual acetaldehyde, and can also result ingreater generation of acetaldehyde downstream from polymer productionper se, for example during the molding of preforms. Titanium catalystsalso impart a distinct yellow cast to the product as well.

U.S. Pat. No. 5,656,716 discloses use of high surface area titaniumcatalysts followed by addition of triphenyl phosphate. Without thetriphenyl phosphate, a high inherent viscosity but distinctly yellowproduct was obtained, while with triphenyl phosphate, less coloredproducts are obtained, but only at a low inherent viscosity, thusrequiring solid stating of these products with its disadvantages.

In WO 02/079310 A2, polyesters are stabilized against generation ofaldehydes through addition of one of a diverse population ofstabilizers, including sterically hindered amines such as Tinuvin® 123or Tinuvin® 622 during initial esterification or transesterification.However, no salts of phosphorus-containing acids with these stabilizersare disclosed, nor is their addition late in a melt-phasepolycondensation process.

In U.S. published application 2002/0198297 A1, nitrogenous stabilizersselected from hydroxylamines, substituted hydroxylamines, nitrones, andamine oxides are employed to scavenge acetaldehyde generated duringextrusion of polyesters or polyamides. No salts made from thesenitrogenous-stabilizers with phosphorus-containing acids are disclosed,nor is addition late in the melt-phase polycondensation stage ofpolyester production.

In World published application 2004/074365 A1, salts are made ofhindered amine light stabilizers (HALS) derivatives and organophosphorusacids. Addition of amine salts to polyesters during the melt-phasemanufacturing is not disclosed, nor is reduction of acetaldehyde.

In copending U.S. application Ser. Nos. 10/639,712; 10/382,103;10/772,121; and 10/393,475, the disclosures of which are eachincorporated herein fully by reference, phosphorus-containing acid saltsof various amines and hindered amines are added during extrusion anddisclosed as useful in maintaining polycarbonate molecular weight duringextrusion of polyester/polycarbonate blends, while reducing color aswell. Addition of amine salts to polyesters during the melt-phasemanufacturing is not disclosed, nor is reduction of acetaldehyde. Itwould be desirable to be able to produce PET and other polyesters withan inherent viscosity suitable for production of food and beveragecontainers, without the necessity for solid stating, which exhibit lowercontent of acetaldehyde, and/or which generate reduced levels ofacetaldehyde during further processing. It would further be desirable toproduce PET in shorter reaction time, due to a more active catalyst thanantimony, while maintaining or improving upon the AA properties of theproduct, with or without solid state polymerization.

SUMMARY OF THE INVENTION

It has now been surprisingly discovered that polyesters susceptible toacetaldehyde formation can be continuously produced in a melt phaseprocess to have high inherent viscosity and low acetaldehyde contentwithout solid stating polymerizing the polyester by polycondensinghydroxyl end groups of an ester linkage containing melt in the presenceof a titanium polycondensation catalyst followed by adding a class ofadditives comprising phosphorus-containing acid salts of amines,preferably hindered amines containing both piperidine and triazinerings, late in the melt-phase polycondensation stager, i.e. after theIt.V. of the polymer melt reaches 0.45 dL/g or higher, preferably 0.60dL/g or higher, most preferably 0.75 dL/g or higher and prior tosolidifying, eg. cutting into pellets. For example, the additives may beadded anywhere between the last reactor and a pelletizer, such as aftera gear pump and prior to a filter. The additive may also be added nearthe end of last reactor. The additive may be introduced as a polymerconcentrate or in a liquid carrier, or may be added neat (withoutdilution). The color of the Ti-catalyzed product is not adverselyaffected by the presence of the additives. If desired, the inherentviscosity may be further elevated by solid state polymerization.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a contour plot of acetaldehyde generation with respect to Ticatalyst level and temperature, without addition of any acetaldehydereducing additive.

FIG. 2 is a contour plot similar to FIG. 1, but with 0.1 wt % ofacetaldehyde-reducing additive.

DETAILED DESCRIPTION OF THE INVENTION

Suitable polyesters are generally known in the art and may be formedfrom aromatic or aliphatic dicarboxylic acids, esters of dicarboxylicacids, anhydrides of dicarboxylic acids, acid chlorides of dicarboxylicacids, glycols, epoxides and mixtures thereof. More preferably thepolyesters are formed from diacids such as terephthalic acid,isophthalic acid, and 2,6-naphthalenedicarboxylic acid, and mixturesthereof, and diols such as ethylene glycol, diethylene glycol,1,4-cyclohexanedimethanol, 1,4-butanediol, and mixtures thereof.

The process of the present invention can produce PET polyesters, whichincludes “modified” polyesters. Examples of suitable polyester polymersmade by the process include polyalkylene terephthalate homopolymers andcopolymers modified with one or more modifiers in an amount of 40 mole %or less, preferably less than 15 mole %, most preferably less than 10mole %. Unless otherwise specified, a polymer includes both itshomopolymer and copolymer variants. The preferred polyester polymer is apolyalkylene terephthalate polymer, and most preferred is polyethyleneterephthalate polymer. By “modified” it is meant that the preferreddiacid component and/or diol component are substituted in part with oneor more different diacid and/or diol components.

For example, the preferred diol component, e.g., ethylene glycol in thecase of PET, may be substituted in part with one or more different diolcomponents, and/or the preferred dicarboxylic acid component, e.g.,terephthalic acid, in the case of PET, may be substituted in part withone or more different dicarboxylic acid components. The mole percentagefor all the diacid component(s) totals 100 mole %, and the molepercentage for the entire diol component(s) totals 100 mole %.

For example, the dicarboxylic acid component of the polyester mayoptionally be substituted with up to about 20 mole percent of one ormore different dicarboxylic acids. Such additional dicarboxylic acidsinclude aromatic dicarboxylic acids preferably having 8 to 14 carbonatoms, aliphatic dicarboxylic acids preferably having 4 to 12 carbonatoms, or cycloaliphatic dicarboxylic acids preferably having 8 to 12carbon atoms. Examples of dicarboxylic acids to be included withterephthalic acid include: phthalic acid, isophthalic acid,naphthalene-2,6-dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid,1,3-cyclohexanedicarboxylic acid, stilbene dicarboxylic acid,cyclohexanediacetic acid, 1,12-dodecanedioic acid,diphenyl-4,4′-dicarboxylic acid, succinic acid, glutaric acid, adipicacid, azelaic acid, sebacic acid, mixtures thereof and the like.Polyesters may be prepared from two or more of the above dicarboxylicacids. Moreover, the foregoing dicarboxylic acids, which exist asstereoisomers, may be in their cis-form, trans-form, or as mixturesthereof.

In addition, the glycol component may optionally be substituted with upto about 20 mole percent, of one or more diols other than ethyleneglycol. Such additional diols include cycloaliphatic diols preferablyhaving 6 to 20 carbon atoms or aliphatic diols preferably having 3 to 20carbon atoms. Examples of such diols include: diethylene glycol,triethylene glycol, 1,4-cyclohexanedimethanol, propane-1,2-diol,propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol,3-methylpentane-2,4-diol, 2-methylpentane-1,4-diol,2,2,4-trimethylpentane-1,3-diol, 2-ethylhexane-1,3-diol,2,2-diethylpropane-1,3-diol, hexane-1,3-diol,1,4-di(hydroxyethoxy)-benzene, 2,2-bis-(4-hydroxycyclohexyl)-propane,2,4-dihydroxy-1,1,3,3-tetramethylcyclobutane,2,2-bis-(3-hydroxyethoxyphenyl)-propane,2,2-bis-(4-hydroxypropoxyphenyl)-propane, 1,2-cyclohexanediol,1,4-cyclohexanediol, mixtures thereof and the like. Polyesters may beprepared from two or more of the above diols. Moreover, the foregoingdiols, which exist as stereoisomers, may be in their cis-form,trans-form, or as mixtures thereof. It should be noted in this respectthat presence of ethylene glycol residues, —OCH₂CH₂O—, is paramount,since in the absence of such residues, acetaldehyde generation is notproblematic.

The resins may optionally contain polyfunctional monomers, e.g.,trifunctional or tetrafunctional comonomers such as trimelliticanhydride, trimellitic acid, trimethylolpropane, pyromelliticdianhydride, pentaerythritol, and the like. However, these are notgenerally preferred, and when used, are generally used in most minoramounts.

The polyester compositions of the invention can be prepared bypolymerization procedures known in the art sufficient to effectesterification and polycondensation. Polyester melt phase manufacturingprocesses include condensation of at least one dicarboxylic acid with atleast one diol, optionally in the presence of esterification catalystsin an esterification zone, followed by polycondensation in the presenceof a polycondensation catalyst in a polymerization zone which may insome instances be divided into a prepolymer zone and in the finishingzone; or ester exchange, usually in the presence of atransesterification catalyst in the ester exchange zone, followed in thepresence of a polycondensation catalyst by a prepolymerization zone andfinishing zone. Each of the polymers obtained may optionally be solidstated according to known methods.

To further illustrate, a mixture of one or more dicarboxylic acids,preferably aromatic dicarboxylic acids, or ester forming derivativesthereof, and one or more diols, are continuously fed to anesterification reactor operated at a temperature of between about 200°C. and 300° C., typically between 240° C. and 290° C., and at a pressureof between about 1 psig up to about 70 psig. The residence time of thereactants typically ranges from between about one and five hours.Normally, the dicarboxylic acid(s) is/are directly esterified withdiol(s) at elevated pressure and at a temperature of about 240° C. toabout 270° C. The esterification reaction is continued until a degree ofesterification of at least 60% is achieved, but more typically until adegree of esterification of at least 85% is achieved to make the desiredmonomer and/or oligomers. The monomer and/or oligomer reaction(s) aretypically uncatalyzed in the direct esterification process and catalyzedin ester exchange processes.

Polycondensation catalysts may optionally be added in the esterificationzone along with esterification/ester exchange catalysts. If the catalystforms an insoluble salt with the dicaroxylic acid(s), the catalyst isadded after the esterification zone. If a polycondensation catalyst wasadded to the esterification zone, it is typically blended with the dioland fed into the esterification reactor. Typical ester exchangecatalysts which may be added to the ester exchange zone or reactor(s),and which may be used separately or in combination, include titaniumalkoxides, tin (II) or (IV) esters, manganese, or magnesium acetates orbenzoates and/or other such catalyst materials as are well known tothose skilled in the art. Phosphorus containing compounds and somecolorants may also be present in the esterification zone. Phosphoruscontaining compounds are not recommended to be present in an esterexchange zone as the ester exchange catalysts will be deactivatedprematurely. To maximize rate and the effectiveness of the salt, it ispreferable to wait and add all the phosphorus in the form of the saltnear or at the end of the melt-phase process.

The resulting products formed in the esterification zone includebis(2-hydroxyethyl) terephthalate (BHET) monomer, low molecular weightoligomers, DEG, and water (or alcohol in the case of ester exchange) asthe condensation by-product, along with other trace impurities formed bythe reaction of the catalyst, if any, or by the reaction of startingmaterials and other compounds such as colorants, impurities in thestarting materials or the phosphorus-containing compounds, if any. Therelative amounts of BHET and oligomeric species will vary depending onwhether the process is a direct esterification process in which case theamount of oligomeric species are significant and even present as themajor species, or an ester exchange process in which case the relativequantity of BHET predominates over the oligomeric species. The water isremoved as the esterification reaction proceeds to drive the equilibriumtoward products. The esterification zone typically produces the monomerand oligomer mixture, if any, continuously in a series of one or morereactors. Alternately, the monomer and oligomer mixture could beproduced in one or more batch reactors. It is understood, however, thatin a process for making PEN, the reaction mixture will contain themonomeric species bis(2-hydroxyethyl)naphthalate and its correspondingoligomers, in lieu of BHET and its corresponding oligomers which will bepresent when making PET.

Once the desired degree of esterification is completed, the reactionmixture is transported from the esterification reactors in theesterification zone to the polycondensation zone, which may comprise aprepolymer zone and a finishing zone. Polycondensation reactions areinitiated and continued in the melt phase in the prepolymerization zoneand finished in the melt phase in the finishing zone, after which themelt is solidified into product, or optionally precursor, solids in theform of chips, pellets, or any other shape. The solids can be optionallycrystallized before or after cutting.

Each zone may comprise a series of one or more distinct reaction vesselsoperating at different conditions, or the zones may be combined into onereaction vessel using one or more sub-stages operating at differentconditions in a single reactor. That is, the prepolymer stage caninvolve the use of one or more reactors operated continuously, one ormore batch reactors, or even one or more reaction steps or sub-stagesperformed in a single reactor vessel. In some reactor designs, theprepolymerization zone represents the first half of polycondensation interms of reaction time, while the finishing zone represents the secondhalf of polycondensation. While other reactor designs may adjust theresidence time between the prepolymerization zone to the finishing zoneat about a 2:1 ratio, a common distinction in many designs between theprepolymerization zone and the finishing zone is that the latter zonefrequently operates at a higher temperature and/or lower pressure thanthe operating conditions in the prepolymerization zone. Generally, eachof the prepolymerization and the finishing zones comprise one or aseries of more than one reaction vessel, and the prepolymerization andfinishing reactors are sequenced in a series as part of a continuousprocess for the manufacture of the polyester polymer.

In the prepolymerization zone, also known in the industry as the lowpolymerizer, the low molecular weight monomers and oligomers arepolymerized via polycondensation to form polyethylene terephthalatepolyester (or PEN polyester, etc.) in the presence of a catalyst. If thepolycondensation catalyst was not added in the esterification stage, thecatalyst is added at this stage to catalyze the reaction between themonomers and low molecular weight oligomers to form prepolymer and splitoff the diol as a by-product. Other compounds such as phosphoruscontaining compounds, cobalt compounds, and colorants can also be addedin the prepolymerization zone. These compounds may, however, be added inthe finishing zone instead of or in addition to the prepolymerizationzone and esterification zone. In a direct esterification process,phosphorus containing compounds are preferably added near the end or atthe end of the melt-phase process in the form of salts of the invention.In a typical DMT-based process, those skilled in the art recognize thatother catalyst material and points of adding the catalyst material andother ingredients such as phosphorus compounds vary from a typicaldirect esterification process.

In the present application, polycondensation takes place in the presenceof a titanium catalyst, preferably in the presence of from about 3 ppm(parts per million) to about 35 ppm of titanium from the catalyst, morepreferably about 6-15 ppm titanium from the catalyst, in each case basedon the weight of titanium in the polymer. During the polycondensation,preferably following completion of 90% or more of the totalpolycondensation time, an amine salt of a phosphorus-containing acid isadded, preferably in amounts to supply of about 250 ppm phosphorus orless, more preferably about 5 to 90 ppm, and most preferably 15 to 80ppm. The amounts are calculated in terms of the weight of elementalphosphorus relative to the weight of the polymer. The mole ratio ofphosphorus to Ti (regardless of oxidation state) is preferably fromabout 1 to about 15, more preferably from 2.5 to 13.

The titanium catalyst may be any titanium compound which exhibits areasonable polycondensation rate. Preferably, the catalyst exhibits atleast the same rate of polycondensation as is achieved using antimonytriacetate or antimony trioxide, and more preferably exhibits aconsiderably greater rate of polycondensation in the absence ofphosphorus compounds, for example a rate from 10 to 50 times higher thanantimony triacetate or antimony trioxide, based in part on the weight ofthe catalytic element relative to the weight of the polymer. It has beenfound, for example, that a polyester of suitable inherent viscosity canbe produced under similar conditions in shorter time than in an antimonycatalyzed polycondensation, while also using much less catalyst. Thetitanium catalyst can be added anywhere in the melt phase process, suchas into the esterification zone or the polycondensation zone. It ispreferably added after at least 90% conversion in the esterificationzone, or after completing esterification (which includes esterexchange), or between the esterification zone and the polycondensationzone, or to the beginning of polycondensation, or duringprepolymerization.

Preferred titanium catalysts include, in general, titanium (IV)compounds which are alkoxides, glycolates, acetates, oxalates, etc.Alkoxides and mixed glycolate alkoxides are preferred. Titanium (IV)isopropoxide is an example of a preferred catalyst. Many such catalystsare available commercially, i.e., under the trademark Tyzor® titanatesfrom DuPont. Solid titanium compounds which serve as heterogenouscatalysts are also suitable, including those disclosed in U.S. Pat. No.5,656,716, incorporated herein by reference. Titanium oxides andhydrated oxides may become solubilized during the course of thepolymerization, for example by complexation and/or reaction with theglycol component. If catalysts remain insoluble, at least in part,catalytic activity would be a concern, as would haze (lack of clarity).Soluble catalysts are preferred, more preferably, those catalysts whichare soluble at the outset of the reaction. The titanium catalysts may beintroduced into the reaction in any convenient manner. A solution of thecatalyst in alcohol or a slurry of the catalyst in ethylene glycol maybe used, for example, as may be a solution or slurry of the catalyst inan oligomer mixture. The catalyst may also be added alone, anddistributed by agitation, i.e., by mechanical mixing or by use of astatic mixer.

This prepolymer polycondensation stage generally employs a series of oneor more vessels and is operated at a temperature of between about 250°C. and 305° C. for a period between about five minutes to four hours.During this stage, the It.V. of the monomers and oligomers is increasedup to about no more than 0.48 dL/g. The diol byproduct is removed fromthe prepolymer melt using an applied vacuum ranging from 4 to 70 torr todrive the reaction to completion. In this regard, the polymer melt issometimes agitated to promote the escape of the diol from the polymermelt. As the polymer melt is fed into successive vessels, the molecularweight and thus the inherent viscosity of the polymer melt increases.The pressure of each vessel is generally decreased to allow for agreater degree of polymerization in each successive vessel or in eachsuccessive zone within a vessel. To facilitate removal of glycols,water, alcohols, aldehydes, and other reaction products, the reactorsare typically run under a vacuum or purged with an inert gas. Inert gasis any gas which does not cause unwanted reaction or productcharacteristics at reaction conditions. Suitable gases include, but arenot limited to argon, helium and nitrogen.

Once an It.V. of no more than about 0.48 dL/g is obtained, theprepolymer is fed from the prepolymer zone to a polycondensationfinishing zone where the polycondensation is continued further in one ormore finishing vessels generally, but not necessarily, ramped up tohigher temperatures than present in the prepolymerization zone, to avalue within a range of from 270° C. to 305° C. until the It.V. of themelt is increased from the It.V. of the melt in the prepolymerizationzone (typically 0.20 to 0.30 dL/g but usually not more than 0.48 dL/g)to an It.V in the range of from about 0.54 dL/g to about 1.2 dL/g. Thefinal vessel, generally known in the industry as the “high polymerizer,”“finisher,” or “polycondenser,” is operated at a pressure lower thanused in the prepolymerization zone, e.g. within a range of between about0.2 and 4.0 torr. Although the finishing zone typically involves thesame basic chemistry as the prepolymer zone, the fact that the size ofthe molecules, and thus the viscosity differs, means that the reactionconditions also differ. However, like the prepolymer reactor, each ofthe finishing vessel(s) is operated under vacuum or inert gas, and eachis typically agitated to facilitate the removal of ethylene glycol.

Once the desired It.V. is obtained in the finisher, the melt isgenerally processed to convert the molten PET into amorphous solidpellets. The technique used for making a pellet is not limited. Asuitable It.V. from the melt phase can range from 0.5 dL/g to 1.15 dL/g.However, one advantage of the present process is that the solid statingstep can optionally be avoided. Solid stating is commonly used forincreasing the molecular weight (and the It.V.) of the pellets in thesolid state, usually by at least 0.05 units, and more typically from 0.1to 0.5 units. Therefore, in order to avoid a solid stating step, apreferred It.V. from the melt phase, which can be measured on theamorphous pellets, is from at least 0.7 dL/g, or at least 0.72 dL/g, orat least 0.75 dL/g, or at least 0.78 dL/g, and up to about 1.15 dL/g to1.20 dL/g.

The method and equipment for converting molten polymer in the melt phasereactors to pellets is not limited, and any conventional system used formaking pellets is suitable in the practice of the invention. Forexample, strands of the polyester polymer melt are at least surfacecooled to below the T_(g) of the polymer to form a cooled polyesterpolymer, followed by pelletizing the cooled polyester polymer to formsolid amorphous pellets. These pellets may be optionally crystallized.Alternatively, the molten polymer may be extruded through a die andinstantly cut into pellets before the polyester polymer cools below itsT_(g). These pellets may be optionally crystallized before the polymercools below its T_(g).

Preferably, the It.V of a polyester of this invention is from about 0.70dL/g to about 1.2 dL/g. The It.V. can be determined from the inherentviscosity is measured at 25° C. using 0.50 grams of polymer per 100 mLof a solvent consisting of 60% by weight phenol and 40% by weight1,1,2,2-tetrachloroethane. The intrinsic viscosity is typically reportedas the It.V. of the polymer, which is a number calculated from themeasured Ih.V. according to the equation set forth in the Examplesection.

Also, although not required, additives normally used in polyesters maybe used if desired. Such additives include, but are not limited tocolorants, pigments, carbon black, glass fibers, fillers, impactmodifiers, antioxidants, stabilizers, flame retardants, reheat aids, andthe like.

In addition, certain agents which color the polymer can be added to themelt. A bluing toner can be added to the melt in order to reduce the b*of the resulting polyester polymer melt phase product. Such bluingagents include blue inorganic and organic toners. In addition, redtoners can also be used to adjust the a* color.

Organic toners, e.g., blue and red organic toners, such as thosedescribed in U.S. Pat. Nos. 5,372,864 and 5,384,377, which areincorporated by reference in their entirety, can be used. The organictoners can be fed as a premix composition. The premix composition may bea neat blend of the red and blue compounds or the composition may bepre-dissolved or slurried in one of the polyester's raw materials, e.g.,ethylene glycol.

Alternatively, or in addition to, inorganic bluing agents can also beadded to the melt to reduce its yellow hue. Cobalt (II) compounds, suchas cobalt (II) carboxylates, are one of the most widely used toners inthe industry to mask the yellow color of polymers. When directesterification is not being used, the cobalt carboxylate can be added tothe ester exchange reactor to also act as an ester exchange catalyst.

The total amount of toner components added depends, of course, on theamount of inherent yellow color in the base polyester and the efficacyof the toner. Generally, a concentration of up to about 15 ppm ofcombined organic toner components and a minimum concentration of about0.5 ppm are used. The total amount of bluing additive typically rangesfrom 0.5 to 10 ppm.

The toners can be added to the esterification zone or to thepolycondensation zone. Preferably, the toners are added to theesterification zone or to the early stages of the polycondensation zone,such as to a prepolymerization reactor.

In one preferred embodiment, the subject process differs substantiallyfrom prior processes in that it is capable of producing a product ofsufficiently high inherent viscosity directly in the melt phase, withoutinvolving any necessity for a subsequent solid state polymerization,usually termed “solid stating.” Avoidance of solid stating also may evenallow direct molding from the melt. These advantages are achievedthrough the use of titanium catalysts in conjunction with amine salts ofphosphorus-containing acids, which are added late in thepolycondensation stage. It has been surprisingly discovered that thepresent method allows a reduced polycondensation time, creates a productof suitable inherent viscosity without solid stating, and produces asolid product exhibiting reduced acetaldehyde content and reducedacetaldehyde generation upon melting.

The amine component of the amine salts of a phosphorus-containing acidcan be chosen from all organic amines capable of salt formation, i.e.primary, secondary, and tertiary organic amines. The amines may becyclic or acyclic, may be monomeric, oligomeric, or polymeric, andshould be selected so as to minimize haze and/or solubility when thelatter are issues. The organic constituents of the amine may inprinciple be any organic group. Organic groups which beartoxicologically suspect groups, or which decompose into toxic substancesare generally undesirable. Groups which generate odiferous substancesupon heating, or which cause excessive coloration, are also generallynot desirable. Ammonia and related compounds like ammonium hydroxide arealso suitable for use in the invention. When used in Ti-catalyzedpolyesters containing —OCH₂CH₂O— in the repeat unit, some salts are moreeffective than others in terms of the % reduction in AA generation uponmelting relative to a control (no additive). The selection of a salt andits amount for a given application depends on the required % reductionin AA generation upon melting. In general, the selected salt is theleast expensive one that will give the required % reduction in AAgeneration upon melting, and the amount of salt is the lowest that willgive the desired % reduction in AA generation upon melting. If reducedAA content rather than AA generation is the requirement, selectionproceeds in an analogous manner.

Suitable organic groups on the amine include linear and branched alkyl,cycloalkyl, aryl, aralkyl, alkaryl, heteroaryl, etc. Each of these typesof organic groups may be substituted or unsubstituted, i.e. withhydroxy, carboxy, alkoxy, halo, and like groups. The organic groups mayalso contain carbonate, keto, ether, and thioether linkages, as well asamide, ester, sulfoxide, sulfone, epoxy, and the like. This list isillustrative and not limiting.

Preferred amines are cyclic amines having a 5 to 7 membered ring,preferably a six membered ring. These rings may constitute a single“monomeric” species, or may be part of a larger oligomer or polymer.

Preferred cyclic amines are hindered amines which have organic groupssubstituted at ring positions adjacent to the ring nitrogen. The ringnitrogen itself may also be substituted, i.e. by alkyl, aryl, aralkyl,alkaryl, and other groups. The hindered amines may also comprise aportion of an oligomeric moiety or polymeric moiety.

Another type of preferred amines are amino acids. Amino acids withdecomposition points at or above polymerization temperatures areespecially preferred. The L-enantiomer, the D-enantiomer or any mixturethereof, including racemic mixtures, may be used. The amine group andthe carboxylic acid group do not have to be attached to the same carbon.The amino acids may be alpha, beta or gamma. Substituted amino acids maybe used. Amino acids with some solubility in water are especiallypreferred as this allows the synthesis of the salt to be done in water,i.e., without VOC's (volatile organic compounds).

The carboxylic acid group of the amino acid opens up the possibilitythat the compound might be reacted into the polyester chain. Reactioninto the polyester chain should result in less volatility and lessextractability. Reaction into the polyester chain can also beaccomplished if the organic portion of the salt contains a hydroxyland/or a carboxyl group. If there is only 1 carboxyl or hydroxyl group,the salt could function as an end-capper. If there are a total of 2reactive groups (carboxyl or hydroxyl), the salt may not always be atthe end of the chain.

The addition point of the phosphorous salt is desirably late in themelt-phase polymerization process. The late addition of the phosphorussalt occurs when the It.V. of the polymer is at least 0.45 dL/g. As theIt.V. target of the product increases, the It.V. of the polymer when thesalt is added also increases due to rate concerns. Various more specificembodiments include adding the salt:

-   -   a. at a location near the end of the finishing reactor or after        the finishing reactor and before the cutter;    -   b. after the It.V. of the polymer has risen to 0.5 dL/g, or to        0.6 dL/g, or to 0.68 dL/g, or to 0.72 dl/g, or to 0.76 dl/g, or        to 0.80 dL/g    -   c. following at least 75% of the polycondensation time, or at        least 80%, or at least 90%, or even at least 95%, of the        polycondensation time. The polycondensation time is the total        time starting from initiating polycondensation to the point in        time at which polycondensation is terminated or when the desired        It.V. is obtained. For purposes of measuring time in this        embodiment, when vacuum is released and the polymer melt exits        the final reactor, the final It.V. is obtained even though it is        recognized that a very minor It.V. lift or break may occur        between the final reactor and cutter;    -   d. to the polyester melt in the melt phase process at a point        within 0.03 dl/g, or within 0.015 dL/g, of the final It.V.        exiting the melt phase process; or    -   e. at a point within 10 minutes of less of solidifying the melt.

Satisfying any of the conditions of these embodiments is deemed to alsosatisfy the condition that the amine salt is added at a point when theIt.V. of the polymer melt is at least 0.45 dL/g.

If the additive is added too early in the polymerization process, asdefined by the ItV of the polymer, it may be more difficult orimpossible to reach a high target ItV in a reasonable process time.Thus, as stated earlier, the additive is incorporated at a late stage inthe polycondensation, preferably in the finisher or just prior topelletization or other means of solidification from the melt to reducethe AA content in the formed solids.

The precursor to the phosphorous moiety of the phosphorus salt may beany oxyphosphorus acid, including but not limited to hypophosphorousacid, phosphorous acid, phosphoric acid, polyphosphoric acid,polyphosphorous acids, pyrophosphoric acid, phosphinic acids, phosphonicacids, phosphate monoesters, phosphate diesters, phosphonate monoesters,pyrophosphate monoesters, pyrophosphate diesters, pyrophosphatetriesters, or salts or compounds which still bear at least one acidhydrogen, etc. The hydrogen on any OH group bound directly to the P═Ogroup is acidic. Compounds with more than one acidic hydrogen may haveone or more acidic hydrogens substituted with organic groups such asalkyl, aryl, aralkyl, alkaryl, etc., by polyether oligomers, polyesteroligomers, etc. At least one salt-forming acidic hydrogen must remain,however. Oxyphosphorus acids with one or more hydrogen bound directly tothe P═O group may have one or more of these hydrogens substituted withorganic groups such as alkyl, aryl, aralkyl, alkaryl, etc. Examples ofthese compounds include but are not limited to alkylphosphonic acids,alkylphosphinic acids and dialkylphosphinic acids. As with the amines,the organic groups may be substituted.

The amines must contain at least one nitrogen capable of salt formationwith a phosphorus-containing acid. In hindered amines containingN-alkylated piperidinyl moieties, for example, salt formation mayinvolve the piperidinyl nitrogen, generating species such as (but notlimited to):

When there is one nitrogen in the amine compound that can form a salt,one mole of phosphorus-containing acid is used per mole of aminecompound. When there are two or more nitrogen atoms in the aminecompound that can form salts, two or more moles of acid can be used permole of amine compound, up to an amount of acid, which creates saltshaving no remaining neutralizable nitrogen, or slightly in excess ofthis amount.

The salts are prepared by the reaction of one or more acidicphosphorus-containing compounds with one or more basic organic compoundscontaining nitrogen, wherein the phosphorus-containing compounds arepreferably selected from compounds having the formulas:

wherein

R₁ and R₂ are independently selected from hydrogen, C₁-C₂₂-alkyl,substituted C₁-C₂₂-alkyl, C₃-C₈-cycloalkyl, substitutedC₃-C₈-cycloalkyl, heteroaryl, and aryl;

n is 2 to 500; and

X is selected from hydrogen and hydroxy;

and wherein the basic organic compounds containing nitrogen are selectedfrom compounds having the formulas:

wherein

R₁ and R₂ are independently selected from hydrogen, C₁-C₂₂-alkyl,substituted C₁-C₂₂-alkyl, C₃-C₈-cycloalkyl, substitutedC₃-C₈-cycloalkyl, heteroaryl, and aryl;

Each of the following types of organic groups may be substituted orunsubstituted, i.e. with hydroxy, carboxy, alkoxy, halo, and/or likegroups, and any combination thereof. The organic groups may also containcarbonate, keto, ether, and thioether linkages, as well as amide, ester,sulfoxide, sulfone, epoxy, and the like. This list is illustrative andnot limiting.

R₃, R₄, and R₅ are independently selected from hydrogen, C₁-C₂₂-alkyl,substituted C₁-C₂₂-alkyl, C₃-C₈-cycloalkyl, and substitutedC₃-C₈-cycloalkyl wherein preferably, at least one of R₃, R₄, and R₅ is asubstituent other than hydrogen; R₃ and R₄ or R₄ and R₅ collectively mayrepresent a divalent group forming a ring with the nitrogen atom towhich they are attached, e.g., morpholino, piperidino and the like;

R₆, R₇, R₈, and R₉ are independently selected from hydrogen,C₁-C₂₂-alkyl, substituted C₁-C₂₂-alkyl, C₃-C₈-cycloalkyl, substitutedC₃-C₈-cycloalkyl, heteroaryl, aryl;

R₁₀ is selected from hydrogen, —OR₆, C₁-C₂₂-alkyl, substitutedC₁-C₂₂-alkyl, C₃-C₈-cycloalkyl, substituted C₃-C₈-cycloalkyl;

R₁₁ is selected from hydrogen, C₁-C₂₂-alkyl, substituted C₁-C₂₂-alkyl,C₃-C₈-cycloalkyl, substituted C₃-C₈-cycloalkyl, heteroaryl, aryl, —Y₁—R₃or a succinimido group having the formula

wherein

R₁₂ is selected from hydrogen, C₁-C₂₂-alkyl, substituted C₁-C₂₂-alkyl,C₃-C₈-cycloalkyl, substituted C₃-C₈-cycloalkyl, heteroaryl, aryl and maybe located at the 3 4 or 5 positions on the aromatic ring;

the —N(R₃)(R₄) group may be located at the 3, 4 or 5 positions on thepyridine ring of nitrogen compound (5);

the —CO₂R₃ and R₁ groups may be located at any of the 2, 3, 4, 5, 6positions of the pyridine ring of nitrogen compound (6);

L₁ is a divalent linking group selected from C₂-C₂₂-alkylene;—(CH₂CH₂—Y₁)₁₋₃—CH₂CH₂—; C₃-C₈-cycloalkylene; arylene; or —CO-L₂-OC—;

L₂ is selected from C₁-C₂₂-alkylene, arylene, —(CH₂CH₂—Y₁)₁₋₃—CH₂CH₂—and C₃-C₈-cycloalkylene;

Y₁ is selected from —OC(O)—, —NHC(O)—, —O—, —S—, —N(R₁)—;

Y₂ is selected from —O— or —N(R₁)—;

R₁₃ and R₁₄ are independently selected from —O—R₂, and —N(R₂)₂;

Z is a positive integer of up to about 20, preferably up to about 6;

m1, is selected from 0 to about 10;

n1 is a positive integer selected from 2 to about 12;

R₁₅, and R₁₆ are independently selected from hydrogen, C₁-C₂₂-alkyl,substituted C₁-C₂₂-alkyl, C₃-C₈-cycloalkyl, substitutedC₃-C₈-cycloalkyl, heteroaryl, aryl, and radical A wherein radical A isselected from the following structures:

Radical A structures wherein * designates the position of attachment.

Preferably at least one of R₁₅ and R₁₆ is an A radical; and wherein theratio of the number of phosphorus atoms in the acidicphosphorus-containing compound to the number of basic nitrogen atoms inthe basic organic compound is about 0.05 to about 2, preferably fromabout 0.25 to about 1.1.

The term “C₁-C₂₂-alkyl” denotes a saturated hydrocarbon radical whichcontains one to twenty-two carbons and which may be straight orbranched-chain. Such C₁-C₂₂ alkyl groups can be methyl, ethyl, propyl,butyl, pentyl, hexyl, heptyl, octyl, isopropyl, isobutyl, tertbutyl,neopentyl, 2-ethylheptyl, 2-ethylhexyl, and the like. The term“substituted C₁-C₂₂-alkyl” refers to C₁-C₂₂-alkyl radicals as describedabove which may be substituted with one or more substituents selectedfrom hydroxy, carboxy, halogen, cyano, aryl, heteroaryl,C₃-C₈-cycloalkyl, substituted C₃-C₈-cycloalkyl, C₁-C₆-alkoxy, C₂-C₆alkanoyloxy and the like.

The term “C₃-C₈-cycloalkyl” is used to denote a cycloaliphatichydrocarbon radical containing three to eight carbon atoms. The term“substituted C₃-C₈-cycloalkyl” is used to describe a C₃-C₈-cycloalkylradical as detailed above containing at least one group selected fromC₁-C₆-alkyl, C₁-C₆-alkoxy, hydroxy, carboxy, halogen, and the like.

The term “aryl” is used to denote an aromatic radical containing 6, 10or 14 carbon atoms in the conjugated aromatic ring structure and theseradicals are optionally substituted with one or more groups selectedfrom C₁-C₆-alkyl; C₁-C₆-alkoxy; phenyl, and phenyl substituted withC₁-C₆-alkyl; C₁-C₆-alkoxy; C₃-C₈-cycloalkyl; halogen; hydroxy, carboxy,cyano, trifluoromethyl and the like. Typical aryl groups include phenyl,naphthyl, phenylnaphthyl, anthryl (anthracenyl) and the like. The term“heteroaryl” is used to describe conjugated cyclic radicals containingat least one hetero atom selected from sulfur, oxygen, nitrogen or acombination of these in combination with from two to about ten carbonatoms and these heteroaryl radicals substituted with the groupsmentioned above as possible substituents on the aryl radical. Typicalheteroaryl radicals include: 2- and 3-furyl, 2- and 3-thienyl, 2- and3-pyrrolyl, 2-, 3-, and 4-pyridyl, benzothiophen-2-yl;benzothiazol-2-yl, benzoxazol-2-yl, benzimidazol-2-yl,1,3,4-oxadiazol-2-yl, 1,3,4-thiadiazol-2-yl, 1,2,4-thiadiazol-5-yl,isothiazol-5-yl, imidazol-2-yl, quinolyl and the like.

The terms “C₁-C₆-alkoxy” and “C₂-C₆-alkanoyloxy” are used to representthe groups —O—C₁-C₆-alkyl and —OCOC₁-C₆-alkyl, respectively, wherein“C₁-C₆-alkyl” denotes a saturated hydrocarbon that contains 1-6 carbonatoms, which may be straight or branched-chain, and which may be furthersubstituted with one or more groups selected from halogen, methoxy,ethoxy, phenyl, hydroxy, carboxy, acetyloxy and propionyloxy. The term“halogen” is used to represent fluorine, chlorine, bromine, and iodine;however, chlorine and bromine are preferred.

The term “C₂-C₂₂-alkylene” is used to denote a divalent hydrocarbonradical that contains from two to twenty-two carbons and which may bestraight or branched chain and which may be substituted with one or moresubstituents selected from hydroxy, carboxy, halogen, C₁-C₆-alkoxy,C₂-C₆-alkanolyloxy and aryl. The term “C₃-C₈-cycloalkylene” is used todenote divalent cycloaliphatic radicals containing three to eight carbonatoms and these are optionally substituted with one or more C₁-C₆-alkylgroups. The term “arylene” is used to denote 1,2-, 1,3-, and1,4-phenylene radicals and these optionally substituted with C₁-C₆—alkyl, C₁-C₆-alkoxy and halogen.

Preferred hindered amines contain alkyl-substituted piperidinyl moietiesand/or triazine moieties, more preferably hindered amines where at leastone amine group is substituted by both a triazine moiety and analkyl-substituted piperidine moiety. In the most preferred hinderedamines, amino group-containing moieties are linked by an alkylene group,preferably a (—CH₂—)_(n) group where n is from 2 to 12, preferably from4-10, and most preferably 6 or 8.

The most preferred hindered amine is Cyasorb® UV-3529, containing repeatunits of the formula:

The salt of the amine component of the novel compositions provided bythe present invention may be prepared by bringing together the acidicphosphorus-containing compound and the basic nitrogen-containing organiccompound in a suitable manner. A suitable manner is any procedure thatinvolves contacting the acidic phosphorus-containing acid with the basicorganic compound. For example, the acidic phosphorus-containing compoundand the basic nitrogen-containing organic compound may be dissolved inappropriate solvents and the solutions mixed followed by precipitationof the reaction product; mixing the phosphorus-containing acid and thebasic organic compound without solvent; and the like.

The ratio of the number of acidic oxyphosphorus groups in the acidicphosphorus-containing compound to the number of basic nitrogen atoms inthe basic organic compound may be in the range of about 0.05 to about 2,preferably from about 0.25 to about 1.1. Compositions that contain alarge excess of unreacted phosphorus-containing acidic compounds mayresult in corrosion of process equipment during polyester manufacture,concentrate manufacture (if any) or preform manufacture.

The salt or salts typically are present in concentrations ranging fromabout 0.0001 to about 0.25 weight percent based on the weight of thepolyester.

The acidic phosphorus-containing compounds preferably are phosphorousacid, phosphoric acid and polyphosphoric acid, most preferablyphosphorous acid and phosphoric acid.

Examples of suitable basic organic compounds containing nitrogen includeamino acids, ammonium salts and alkyl amines such as triethylamine and2,2,6,6-tetramethylpiperidine, pyridine and substituted pyridines,piperidine and substituted piperidines, morpholine and substitutedmorpholines and the like. The preferred basic organic compounds arehindered amine light stabilizers (HALS) such as: Cyasorb UV-3346 (CytecIndustries, CAS#90751-07-8), Cyasorb UV-3529 (Cytec Industries,CAS#193098-40-7), Cyasorb UV-3641 (Cytec Industries, CAS#106917-30-0),Cyasorb UV-3581 (Cytec Industries, CAS#79720-19-7), Cyasorb UV-3853(Cytec Industries, CAS#167078-06-0), Cyasorb UV-3853S (Cytec Industries,CAS#24860-22-8), Tinuvin 622 (Ciba Specialty Chemicals, CAS#65447-77-0),Tinuvin 770 (Ciba Specialty Chemicals, CAS#52829-07-9), Tinuvin 144(Ciba Specialty Chemicals, CAS#63843-89-0), Tinuvin 123 (Ciba SpecialtyChemicals, CAS#129757-67-1), Chimassorb 944 (Ciba Specialty Chemicals,CAS#71878-19-8), Chimassorb 119 (Ciba Specialty Chemicals,CAS#106990-43-6), Chimassorb 2020 (Ciba Specialty Chemicals,CAS#192268-64-7), Lowilite 76 (Great Lakes Chemical Corp.,CAS#41556-26-7), Lowilite 62 (Great Lakes Chemical Corp.,CAS#65447-77-0), Lowilite 94 (Great Lakes Chemical Corp.,CAS#71878-19-8), Uvasil 299LM (Great Lakes Chemical Corp.,CAS#182635-99-0), and Uvasil 299HM (Great Lakes Chemical Corp.,CAS#182635-99-0), Dastib 1082 (Vocht a.s., CAS#131290-28-3), Uvinul4049H (BASF Corp., CAS#109423-00-9), Uvinul 4050H (BASF Corp.,CAS#124172-53-8), Uvinul 5050H (BASF Corp., CAS#199237-39-3), Mark LA 57(Asahi Denka Co., Ltd., CAS#64022-61-3), Mark LA 52 (Asahi Denka Co.,Ltd., CAS#91788-83-9), Mark LA 62 (Asahi Denka Co., Ltd.,CAS#107119-91-5), Mark LA 67 (Asahi Denka Co., Ltd., CAS#100631-43-4),Mark LA 63 (Asahi Denka Co., Ltd. Co., Ltd. Co., CAS#115055-30-6), MarkLA 68 (Asahi Denka Co., Ltd., CAS#100631-44-5), Hostavin N 20 (ClariantCorp., CAS#95078-42-5), Hostavin N 24 (Clariant Corp., CAS#85099-51-1,CAS#85099-50-9), Hostavin N 30 (Clariant Corp., CAS#78276-66-1),Diacetam-5 (GTPZAB Gigiena Truda, USSR, CAS#76505-58-3), Uvasorb-HA 88(3V Sigma, CAS#136504-96-6), Goodrite UV-3034 (BF Goodrich Chemical Co.,CAS#71029-16-8), Goodrite UV-3150 (BF Goodrich Chemical Co.,CAS#96204-36-3), Goodrite UV-3159 (BF Goodrich Chemical Co.,CAS#130277-45-1), Sanduvor 3050 (Clariant Corp., CAS#85099-51-0),Sanduvor PR-31 (Clariant Corp., CAS#147783-69-5), UV Check AM806 (FerroCorp., CAS#154636-12-1), Sumisorb TM-061 (Sumitomo Chemical Company,CAS#84214-94-8), Sumisorb LS-060 (Sumitomo Chemical Company,CAS#99473-08-2), Uvasil 299 LM (Great Lakes Chemical Corp.,CAS#164648-93-5), Uvasil 299 HM (Great Lakes Chemical Corp.,CAS#164648-93-5), Nylostab S-EED (Clariant Corp., CAS#42774-15-2).Additional preferred hindered amine light stabilizers may be listed inthe Plastic Additives Handbook 5^(th) Edition (Hanser GardnerPublications, Inc., Cincinnati, Ohio, USA, 2001).

The hindered amine light stabilizers having above formulas (2), (3),(7), (8), (9), (12), (13), (14), (15), (16), (17), (18), (19) and (20),and especially (21), represent the preferred basic compounds. Chimassorb944 (Ciba Specialty Chemicals, CAS#71878-19-8), Cyasorb UV-3529 (CytecIndustries, CAS#193098-40-7), Chimassorb 119 (Ciba Specialty Chemicals,CAS#106990-43-6) and Tinuvin 770 (Ciba Specialty Chemicals,CAS#52829-07-9) and any equivalents thereof are specific examples of thepreferred basic compounds. A more preferred groups of the basic nitrogencompounds are the hindered amine light stabilizers having above formulas(2), (3), (7), (8), (9), (12), (13), (14), (15), (16), (17), (18) and(19) wherein radical R¹⁰ is hydrogen or C1-C22 alkyl and formula (15)wherein at least one of R¹⁵ and R¹⁶ represents radical A wherein R¹⁰ ishydrogen or C1-C22 alkyl. The most preferred are high molecular weightHALS wherein the molecular weight is greater than about 1000 such asCyasorb UV-3529 (Cytec Industries, CAS#193098-40-7). The most preferredHALS correspond to formula (12) set forth above whereinR⁶=R⁷=R⁸=R⁹=R¹⁰=methyl, (R³)(R⁴)N— collectively represent morpholino, L₁is C₁ to C₆ alkylene, and Z is 1 to 6. Additionally, the hindered aminelight stabilizers having above formulas (12), (13), (14), (15), (16),(17), (18) and (19) wherein radical R¹⁰ is hydrogen or C1-C22 alkyl andformula (15) wherein at least one of R¹⁵ and R¹⁶ represents radical Awherein R¹⁰ is hydrogen or C1-C22 alkyl are particularly preferred asthe basic organic component of a salt with an oxyphosphorus acid, whichcan be used to lower residual AA in pellets and/or AA generation uponmelting for polyester compositions containing —OCH₂CH₂O— in a repeatunit.

Examples of suitable amines include ammonia and its salts, alkyl andcycloalkyl amines such as methylamine, ethyl amine, n-propylamine,i-propylamine butylamine, n-hexylamine, 2-ethylhexylamine,dimethylamine, diethylamine, di(n-propyl)amine, di(i-propyl)amine,di-(n-hexyl)amine, di(n-octyl)amine, cyclopentylamine,dicyclopentylamine, cyclohexylamine, dicyclohexylamine,cycloheptylamine, cyclooctylamine, adamantane amine, trimethylamine,triethylamine, tri(n-butyl)amine, ethylene diamine,1,3-propylenediamine, triethylenediamine, and polyalkylenepolyamines ingeneral, diethanolamine, dipropanolamine, triethanolamine,tripropanolamine, fatty amines, di(fatty)amines, and the like.

Hetrocyclic amines include piperine, piperidine, morpholine,aminopyridine, and in particular, heterocyclic, non-aromatic aminessubstituted in one or more ring positions adjacent to the ring nitrogen,for example 2,6-dimethylpiperidine, 2-methyl-6-ethylpiperidine,2,6-di(isopropyl)piperidine, 2,2,6,6-tetramethyl piperidine, and thelike. The same types of substitution patterns are useful with othercyclic amines. The substituent and substituent patterns are illustrativeand not limiting.

In general, it is preferred that the amines used be of relatively highvapor pressure, and thus it is not preferred to employ low molecularweight alkylamines such as methylamine, dimethylamine, ethylamine, andthe like, since they may be lost due to volatility when the position ofthe equilibrium results in the unsalted form and/or these might pose amigration problem. Low molecular weight alkylamines that are substitutedwith carboxy and/or hydroxyl functionality(ies), which may react intothe polyester chain, are preferred. Amino acids are examples of thisclass of compounds. The inner salt nature of amino acids results in highmelting/decomposition points and, in some cases, gives some solubilityin water, which eliminates volatile organic compounds (VOC) during thesalt synthesis.

By utilizing the process of the present invention, polymers withsuitably high It.V. may be obtained in relatively short overall processtimes, and produce polyester product, for example in the form ofpellets, which not only do not require the expense and increased processtime of solid stating, but also contain less AA and generate less AAduring future processing. If yet higher It.V. polymers are desired, themolecular weight may be increased further by solid stating. While thisadditional process step does involve extra time and expense, this ispartially compensated by reduction in overall polymerization time in themelt phase. Moreover, solid stating will further reduce the AA content.Immediately following the finishing reactor and before pelletization,the amine salts of the invention may be added to molten polyester andblended with a static mixer or any effective mixing apparatus.Alternatively, the amine salts may be added near the end of the finisherreactor. In either case, the amine salts may be added neat (withoutdilution), in a slip stream of molten polyester, as a master batch inpolyester pellets, i.e. a concentrate, or in a liquid carrier. Thepolyesters according to the present invention can be used in forming avariety of articles including sheets, films, tubing, profiles, preforms,fibers, woven and shaped articles, such as containers, and thermoformedarticles such as trays and the like.

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples which are providedherein for purposes of illustration only and are not intended to belimiting unless otherwise specified.

EXAMPLES

Free acetaldehyde content in the polymer following addition of therespective additives is assessed as follows. Following the end of thearray or lab preparation, the polymer is cooled for about 15 min.,separated from the glass flask, cooled for about 10 min. and then placedimmediately into liquid nitrogen. The polymer is ground cryogenically topass a 3 mm screen. The residual or free AA sample is kept frozen.

For preforms, it is sufficient to use ASTM #F2013-00 described below.Since the polymer is melted in an extruder prior to injection molding,there is an opportunity for any AA precursors to be converted to AA.When experimental PET samples are prepared in the laboratory, there isusually not enough material to mold performs to test AA. ExperimentalPET samples prepared in the laboratory are in the form of pellets orpowders (most common). In the case of PET pellets or powders, there hasbeen no melting after the manufacturing; therefore to give the samples amelt heat history, pellets or powders are melted during the AAgeneration test described below prior to testing free AA by ASTM#F2013-00. The AA level from ASTM #F2013-00 on preforms cannot becompared directly to the AA level from the AA generation test on pelletsor powders; however, two methods are correlated, and similar trendsshould be seen in each test. A commercial polyester sold to makecarbonated soft drink (“CSD”) bottles (CB-12) is submitted every timethe AA generation test is done on experimental samples. The AA level inpreforms made from commercial pellet samples is usually well known attypical processing conditions and considered acceptable for CSDapplications. The AA generation results on the commercial polyester areconsidered as a benchmark: AA generation rates less than or equal to theAA generation value of the commercial pellets should indicate anacceptable level of preform AA for CSD applications at the time that thetesting was done. The water bottle market can necessitate lower AAgeneration rates than those acceptable in the CSD bottle market.

The acetaldehyde generation rate can be measured on the solid particlesand the free AA can be measured on solid particles or preforms. Thefollowing method is used to measure acetaldehyde generation on solidparticles.

The method used to determine the level of free AA in the polyesterpolymer composition is the test method ASTM #F2013-00. This test methodis used to measure the level of free acetaldehyde in particles, powders,preforms, bottles, and any other form the polyester polymer compositionmay take. For purposes of measuring residual or free acetaldehyde, thesample is tested according to the method described below. However, forpurposes of measuring the acetaldehyde generation, the sample has toundergo a second melt history in order to determine the level ofacetaldehyde generated. If the sample is a particle or powder which hasnot undergone a melt step in addition to a prior melt phasepolycondensation step, the sample is first treated according to theSample Preparation procedure described below, after which the sample issubmitted to the ASTM #F2013-00 test method for analysis.

The test procedure for measuring the level of free acetaldehyde on asample, whether a preform, pellet, powder, or other form is the ASTM#F2013-00 test method. Samples are cryogenically ground through a WileyMill equipped with a 1.0 mesh screen. The final ground material has aparticle size less than 800 μm. A portion of a sample (0.20 g) isweighed into a 20-mL head-space vial, sealed and then heated at 150° C.for sixty minutes. After heating, the gas above the sealed sample of PETpolymer is injected onto a capillary GC column. The acetaldehyde isseparated, and the ppm of acetaldehyde present in the sample is thencalculated. The amount of acetaldehyde calculated represents the amountof free or residual acetaldehyde present in the sample.

To obtain the acetaldehyde generation rate, the ASTM #F2013-00 testmethod as described above is also used, except that prior to testing thesample by the ASTM #F2013-00 test method, it undergoes a melt history inaddition to the previous melt phase polycondensation. For measuring theacetaldehyde generation rate on preforms, it is sufficient to use thisASTM #F2013-00 Method as described above without subjecting the preformsto a further melt history since by virtue of making a preform, thepellets are melted in an extruder prior to injection molding. By meltextruding or injection molding, AA precursors in the polymer melt havethe opportunity to covert to acetaldehyde. In the event that the sampleis a particle or a powder which has not seen a subsequent melt history,the sample is prepared according the Sample Preparation method, and thensubmitted to the ASTM #F2013-00 test. Sample Preparation: For thepurpose of measuring the acetaldehyde generation rate, and if the samplehas not seen a melt history subsequent to melt phase polycondensation,it is prepared according to this method prior to submitting the sampleto the ASTM #F2013-00 test. Samples of polymer powder ground to pass a 3mm screen are heated in an oven at 115° C. under vacuum (25-30 in. Hg)with a 4 SCFH nitrogen purge for at least 48 h. Although overnightdrying would be sufficient for water removal alone, this extended oventreatment also serves to desorb to about 1 ppm or less the residual AApresent in the high IV powder after melt-phase-only synthesis and priorto AA generation testing. It would take longer to desorb residual AAfrom pellets to about 1 ppm or less, due to the larger particle size(longer diffusion path). Any suitable acetaldehyde devolatizationtechnique can be employed on pellets which reduces the level of freeacetaldehyde down to about 1 ppm or less, including passing hot inertgas over the pellets for a time period sufficient to reduce the residualacetaldehyde to the desired level. The acetaldehyde devolatizationtemperature should not exceed 170° C. The sample is then packed in apreheated Tinius Olsen extrusion plastometer using a steel rod. Theorifice die is calibrated according to ASTM D 1238. A small amount ofmaterial is purged out the bottom, which is then plugged. The piston rodassembly is put in the top of the barrel. A 225 g weight may be placedon top of the piston rod to hold the rod down inside of the barrel. Thepolymer is held at 295° C. for 5 min. The orifice plug is then removedfrom the bottom of the barrel. Via a large weight and operator pressure,the extrudate is pushed out of the barrel into an ice water bath. Theextrudate is patted dry, sealed in a bag and placed in a freezer untilthe ASTM #F2013-00 test is performed.

Alternatively, a CEAST Model 7027 Modular Melt Flow instrument is used.An AA generation program is initiated that will maintain a temperatureof 295° C. and will extrude the melted PET material in 5 minutes at aconstant flow rate as defined in the firmware of the instrument. As theextrudate is pushed out of the barrel and into an ice water bath, thesample is collected, patted dry, sealed in a bag and placed in a freezeruntil the ASTM #F2013-00 test is performed.

Acetaldehyde can be generated in polyester resins with the Ceast Model7027 Modular Melt Flow or any similar extrusion plastometer instrument.The automated functions of this instrument reduce test variability bymaintaining consistent contact times for the polymer inside theextrusion barrel. This particular model of instrument incorporatesautomated packing of the resin at the start of the test procedure. Theinstrument is equipped with a motorized platform that will push thematerial out of the barrel until the piston is at a specified heightabove the bottom of the barrel. The platform will then hold the pistonrod in place, allowing the resin to heat up and generate acetaldehyde.At the end of the specified hold time, the platform extrudes theremainder of the resin out of the barrel while traveling at a constantspeed. These steps eliminate the possibility of variability in resultsfrom packing the material through the final extrusion step. Variabilityin loading the polymer is reduced with the design of the barrel, but isnot automated.

Acetaldehyde can be generated in the above manner over a temperaturerange of 265° C. to 305° C. The most consistent results are obtainedbetween 285° C. and 295° C. The length of time the resin is held insidethe barrel shows good results when between 2 and 15 minutes. The rangeof 5 to 10 minutes shows the best repeatability and distinction betweenmaterials. For the AA generation numbers stated for this invention, 295°C. and 5 minutes were used.

Use of this method of acetaldehyde generation and testing allows forscreening of polyester resins for acetaldehyde generation withoutneeding large amounts of material for evaluations such as molding ofbottle preforms. As little as 10 grams of material may be used in thisprocess making it ideal for testing laboratory samples.

Other polymer parameters may be measured by standard methods.

The measurements of L*, a* and b* color values are conducted onpolyester polymers ground to a powder passing a 3 mm screen. Colormeasurements were performed in reflectance (specular included) using aHunterLab UltraScan XE (Hunter Associates Laboratory, Inc., Reston Va.),which employs diffuse/8° (illumination/view angle) sphere opticalgeometry. Results were reported using the CIELAB scale with the D65illuminant and 100 observer. The spectrophotometer is standardizedregularly and UV control was employed and maintained in calibrationfollowing the HunterLab recommendations. An optional glass port plate isinstalled at the reflectance port to minimize contamination of thesphere. Powders are placed in an optical glass cell. The optical-gradeglass is recessed from the front of the cell by 0.062″ and the glassitself is 0.092″ thick. The sample area is 0.71″ deep, 1.92″ wide, 2.35″tall. The powders are allowed to settle by vibrating the sample for 20seconds using a laboratory Mini-Vortexer (VWR International, WestChester, Pa.). The glass cell is maintained flush against thereflectance port and covered with a black opaque cover. A single cellpacking is evaluated and the cell is removed and replaced for threereplicate measurements for each sample. The reported value should be theaverage of the triplicates.

The It.V. values described throughout this description are set forth indL/g units as calculated from the inherent viscosity measured at 25° C.in 60% phenol and 40% 1,1,2,2-tetrachloroethane by weight. Polymersamples are dissolved in the solvent at a concentration of 0.25 g/50 mL.The viscosity of the polymer solutions is determined using a ViscotekModified Differential Viscometer. A description of the operatingprinciple of the differential viscometers can be found in ASTM D 5225.The inherent viscosity is calculated from the measured solutionviscosity. The following equations describe such solution viscositymeasurements and subsequent calculations to Ih.V. and from Ih.V. toIt.V:

η_(inh)=[ln(t _(s) /t _(o))]/C

where

-   -   η_(inh)=Inherent viscosity at 25° C. at a polymer concentration        of 0.5 g/100 mL of 60% phenol and 40% 1,1,2,2-tetrachloroethane        by weight    -   ln=Natural logarithm    -   t_(s)=Sample flow time through a capillary tube    -   t_(o)=Solvent-blank flow time through a capillary tube    -   C=Concentration of polymer in grams per 100 mL of solvent        (0.50%)

The intrinsic viscosity is the limiting value at infinite dilution ofthe specific viscosity of a polymer. It is defined by the followingequation:

$\eta_{int} = {{\lim\limits_{Carrow 0}( {\eta_{sp}/C} )} = {\lim\limits_{Carrow 0}{( {\ln \; \eta_{r}} )/C}}}$

where

-   -   η_(int)=Intrinsic viscosity    -   η_(r)=Relative viscosity=t_(s)/t_(o)    -   η_(sp)=Specific viscosity=η_(r)−1

Instrument calibration involves triplicate testing of a standardreference material and then applying appropriate mathematical equationsto produce the “accepted” Ih.V. values. The three values used forcalibration shall be within a range of 0.010; if not, correct problemsand repeat testing of standard until three consecutive results withinthis range are obtained.

Calibration Factor=Accepted Ih.V. of Reference Material/Average ofTriplicate Determinations

The uncorrected inherent viscosity (η_(inh)) of each sample iscalculated from the Viscotek Model Y501 Relative Viscometer using thefollowing equation:

ηinh=[ln(P ₂ /KP ₁)]/C

where

-   -   P₂=The pressure in capillary P₂    -   P₁=The pressure in capillary P₁    -   ln=Natural logarithm    -   K=Viscosity constant obtained from baseline reading    -   C=Concentration of polymer in grams per 100 mL of solvent        The corrected Ih.V., based on calibration with standard        reference materials, is calculated as follows:

Corrected Ih.V.=Calculated Ih.V.×Calibration Factor

The intrinsic viscosity (It.V. or η_(int)) may be estimated using theBillmeyer equation as follows:

η_(int)=0.5[e ^(0.5×Corrected Ih.V.)−1]+(0.75×Corrected Ih.V.)

The reference for estimating intrinsic viscosity (Billmeyerrelationship) is J. Polymer Sci., 4, pp. 83-86 (1949).

Comparative Example A

A sample of PET oligomer prepared from terephthalic acid and ethyleneglycol, and also containing about 1.5 mole percent of about 35% cis/65%trans 1,4-cyclohexanedimethanol was employed in the polycondensation.The oligomer also contains about 1.2 weight percent of diethyleneglycol, which was generated during esterification. This oligomer hasabout 95% conversion of acid groups via NMR/titration of acid groups, aM_(n) of about 766 g/mole, and a M_(w) of 1478 g/mole.

For polycondensation, ground oligomer (103 g) is weighed into ahalf-liter, single-necked, round-bottomed flask. The catalyst employedis titanium tetrabutoxide and it is added to the flask. A 316 Lstainless steel paddle stirrer and glass polymer head were attached tothe flask. After attaching the polymer head to a side arm and a purgehose, two nitrogen purges are completed. The polymerization reactor isoperated under control of a CAMILE™ automation system, programmed toimplement the following array (Table 1).

TABLE 1 Temper- Stir Time ature Vacuum Speed Power Stage (minutes) ° C.(torr) (rpm) (kg-cm) Flags 1   0.1 270 730  0 2 10 270 730  150* 3  2270  140*  300* 4  1 270 140 300 Calibrate 5 10 270  25* 300 6 10 270 25 300 7  1 270  140* 300 8  2 270 140 300 Catalyst (P) 9  1 270  25*300 10 10 270  25 300 11  2 270   2*  30* 12  1 270    0.5*  30 Vacuum13 500# 270    0.5  30 target Power *= ramp; #= torque termination whentemperature = 300° C., change all 270 to 300 (same for 285).

A molten bath of Belmont metal is raised to surround the flask, and theCAMILE™ array is implemented. In this array, a “ramp” is defined as alinear change of vacuum, temperature, or stir speed during the specifiedstage time. The stirring system is automatically calibrated betweenstages 4 and 5. After stage 6 ends, the vacuum level was ramped up to140 torr, and then a 2 minute phosphorus addition stage (stage 8)begins. A phosphorus compound (not the amine salt of the presentinvention) is only added to the Sb controls. The finisher stage (13) isterminated when the stirrer torque is such that it reaches the target(predetermined for a given temperature and polymer rig) three times. Thefinisher stage time is referred to as “Time to IV.” Following the end ofthe array or lab preparation, the polymer is cooled for about 15 min.,separated from the glass flask, cooled for about 10 min. and then placedimmediately into liquid nitrogen. The polymer is ground cryogenically topass a 3 mm screen. The residual or free AA sample is kept frozen.

The ground polymer is analyzed for acetaldehyde generation rate (AAGen),inherent viscosity, L*, a*, and b* color. The data can be seen in Table2. The contour plot of FIG. 1 indicates the acetaldehyde generation rate(at 295° C. for 5 minutes) for different combinations of titanium levelsand polycondensation temperatures at a vacuum level of 1.1 torr. Theaverage AAGen of commercial PET pellets at the same time was 25.5 ppm.None of these are subject invention Examples; all are Comparativeexamples.

TABLE 2 Time AA L* a* b* Ti Temp Vac. to IV IhV Gen Color Color ColorEx. ppm deg C. torr (min) dL/g 295/5 ppm CIELAB CIELAB CIELAB Control¹285 1.1 103.32 0.805 29.35 78.45 −1.99 3.00 C1 10 285 1.1 45.38 0.79637.565 81.85 −1.06 11.18 C2 15 270 2 158.97 0.803 41.255 81.40 −1.3612.48 C3 10 285 1.1 57.12 0.838 38.93 78.73 −0.80 12.32 C4 15 300 0.29.47 0.791 40.805 82.34 −1.52 14.15 C5 5 270 0.2 123.64 0.795 28.3478.59 −0.41 8.65 C6 5 300 2 54.77 0.831 38.52 81.73 −1.31 13.04 C7 10285 1.1 56.5 0.829 39.93 82.08 −1.11 13.38 Control 285 1.1 91.46 0.77134.405 76.73 −1.07 2.65 Control 285 1.1 93.04 0.789 30.97 79.47 −1.952.61 C8 5 270 2 223.17 0.781 23.96 81.13 −0.69 10.58 C9 5 300 0.2 30.080.805 38.465 82.32 −1.37 10.55 C10 15 270 0.2 51.43 0.766 40.72 79.49−0.34 10.44 C11 15 300 2 16.22 0.771 46.15 78.61 −0.31 14.00 C12 10 2851.1 49.39 0.834 28.13 81.36 −0.21 12.06 Control 285 1.1 106.01 0.80732.415 78.37 −0.85 5.66 C13 10 285 1.1 43.4 0.792 38.005 78.23 −0.1210.81 C14 10 285 1.1 51.92 0.852 28.21 78.43 −0.17 10.89

Example A

To make the phosphorous acid salts of CyasorbUV 3529, two moles ofphosphorous acid were used per mole of CyasorbUV 3529, and reacted perthe following procedure. The salts can be manufactured according to thedescription in per copending U.S. application Ser. Nos. 10/39,2575),which is fully incorporated herein by reference

To a 5-L, round-bottomed flask equipped with a mechanical stirrer,thermocouple, and a heating mantle is added 411.76 g of Cyasorb UV-3529and 945 g of toluene. Cyasorb UV-3529 is a polymeric hindered aminelight stabilizer believed to conform generally to the compounds of amineformula (12) set forth above R₆=R₇=R₈=R₉=R₁₀=methyl; L₁ ishexamethylene; and (R₃)(R₄)N— collectively represent a morpholino group.The slurry is heated to 60° C. and stirred until a homogeneous solutionwas obtained. Isopropyl alcohol (370 g) is added to the reaction vessel.A solution of 115.46 g (1.41 mol) of phosphorous acid dissolved into 370g of isopropyl alcohol is added in a small steady stream (fast dropwise)via an addition funnel to the Cyasorb UV-3529 solution with rapidstirring over approximately 30 minutes. A homogeneous solution isobtained and stirred for 15 min once the addition is complete. Thereaction mixture was pumped at about 5 mL/min into a 12 L reactionvessel that contained about 7 L of rapidly stirred heptane (4768 g) overa period of approximately 50 minutes. The feed rate of the reactionmixture into the heptane-containing vessel has some affect on theparticle size of the final product. Slow feeds tend to produce a finerpowder while higher feed rates will results in a larger particle thatalmost appears to be agglomerated. This needs to be balanced by thetendency for the salt to get sticky in the drowning vessel if the feedrate is too rapid. After addition was complete, the resulting slurry wasstirred for about 60 minutes. The precipitate was collected by suctionfiltration. The filter cake was washed twice with 137 g of heptane andthen sucked dry on the filter paper overnight. The solid was placed in ametal pan and dried overnight in a vacuum oven at 50° C. with a slightingress of dry nitrogen. The dry product weighed approximately 531.8 g(101% of theory). Typical bulk density of the dry salt has been between0.4 and 0.6 g/mL.

To test the phosphorous acid salts of Cyasorb UV3529, melt blending in aglass flask achieves a uniform distribution of additive within thepolymer simulating the mixing of an additive near the end of or afterthe final polycondensation reactor. The polyester powders prepared aboveare weighed into 500 mL round bottom flasks. The powders are dried at120° C. under full vacuum overnight (about 16 hours) in a vacuum oven.After cooling the flask to about room temperature in a desiccator (about1.5 hours), the additive is weighed into the flask. The additive wastargeted at the 0.1 wt. % level. The blending parameters are set forthin Table 3.

For mixing the amine salts with the polymers of Table 2, a polymer headwith stirrer is attached and the flask purged twice with nitrogen. TheCAMILE™ automation system is programmed for the following array, as setforth in Table 3.

TABLE 3 Time Temp. Vac Stir Power Estimated Stage Min. ° C. Torr RPMkg-cm End Time 1 .1 270 730 0 0 10:23:59 2 5 270 730 0 0 10:28:59 3 5270 730 0 0 10:33:59 4 5 270 730 15* 0 10:38:59 5 4 270 730 35* 010:42:59 6 2 270 730 75* 0 10:44:59 7 5 270 730 75  0 10:49:59 *= ramp

A moderate nitrogen purge was employed at all times. During Stages 2 and3, the stirrer is turned slowly by hand. Following the end of the array,the polymer is cooled, chopped, and ground to pass a 3 mm screen. Theground polymer is analyzed for acetaldehyde generation rate, inherentviscosity, L*, a*, and b* color. Inherent viscosity is measured at 25°C. on a 0.50 g sample dissolved in 100 mL of 60% by weight phenol and40% by weight 1,1,2,2-tetrachloroethane. The results are presented inTable 4

TABLE 4 Polymer Wt. P IV after in after L* a* b* Ti Temp Vac Blend BlendAdditive Blend after after after Ex. ppm deg C. torr dL/g (g) (g) ppmBlend Blend Blend 1 10 285 1.1 0.752 45 0.048 44 80.68 −0.77 10.57 2 15270 2 0.761 45 0.047 54 80.63 −0.82 11.05 3 10 285 1.1 0.797 45 0.045 4778.78 −0.49 11.65 4 15 300 0.2 0.718 45 0.045 54 80.24 −1.26 13.12 5 5270 0.2 0.785 32.07 0.032 79.61 −0.85 8.96 6 5 300 2 0.778 45 0.045 5279.41 −1.02 13.26 7 10 285 1.1 0.773 45 0.046 51 79.58 −0.85 12.00 8 5270 2 0.735 45 0.045 52 80.69 −0.43 9.98 9 5 300 0.2 0.779 44.93 0.04546 79.83 −1.24 10.97 10 15 270 0.2 0.721 45 0.044 51 79.29 −0.31 8.77 1115 300 2 0.76 45 0.045 52 78.81 −0.73 12.92 12 10 285 1.1 0.78 45 0.04650 81.07 −0.83 11.23 13 10 285 1.1 0.769 45 0.046 47 78.57 −0.53 10.7214 10 285 1.1 0.804 45 0.045 48 78.49 −0.58 10.66

The contour plot of FIG. 2 illustrates the AA generation rates at 295°C. after 5 minutes, after blending about 0.1 wt. % of the phosphorousacid salts of Cyasorb UV 3529 into PET made with various Ti levels,temperature and vacuum levels. This contour plot demonstrates thedramatic improvement in AA generation rate with the additive present ascompared to the previous contour plot (FIG. 1), which was prior toblending in the additive. Reductions in the AA generation rate rangedfrom 75 to 83%. These were calculated per the method described inExample B. The average AAGen of commercial PET pellets tested at thesame time was 24.8 ppm, much higher than the examples with the additive.The examples with the additive have low enough AA generation rates uponmelting to be used in water bottle applications and/or or dual water/CSDapplications. A slight improvement in yellowness or b* color was seenwith about 0.1 wt. % of the additive present.

Examples B

These examples use the melt-blending procedure outlined in Table 3 forthe previous examples, and utilized 100 g of PET modified with about 2.6mole % isophthalic acid and about 4.2 mole % diethylene glycol. This PETwas produced on a production scale line with 10 ppm Ti and 0 ppm P.Examples prefaced with the letter “C” are comparative examples.

The % reduction in AA generation at 295° C. for 5 minutes (AA GEN 295/5)was calculated as follows: 1) an average AAGen for the runs with noadditive was calculated to be 35.68 ppm, 2) the AAGen for a given runwas divided by 35.68 ppm, 3) the quotient was multiplied by 100, and 4)the product was subtracted from 100. As can be seen from the Table 5, %reduction in AA GEN 295/5 was around 75% for around 55 ppm P fromphosphorous acid salts of Cyasorb UV 3529 (“Cyasorb UV 3529-H3PO3”). Theaverage AAGen of production control PET pellets tested at the same timewas 23.5 ppm, much higher than the 8.5-9.3 ppm in the examples with anadditive of this invention. The average L* color of the blends withphosphorus-containing additives were brighter by about one L* unit thanthe average of those without the additive. The average a* color of theblends with phosphorus-containing additives were more green by about0.4a* unit than those without the additive. The average b* color of theblends with phosphorus-containing additives were less yellow by aboutone b* unit than the average of those without additive. On average, theinherent viscosities dropped moderately (<0.05 dL/g) at the additivelevels tested.

Example C

This example uses the melting blending procedure in Table 3 and thepolymer described in Example B.

A further series of polymers were prepared, employing the samephosphorous acid salt of CYASORB UV 3529 as used in the previous ExampleA and Example B. The results are presented in Table 6.

TABLE 5 AA % Amt. GEN Reduction Ti P Added IV 295/5 In AA AVG AVG AVGExample Additive (ppm) (ppm) (g) (dL/g) (ppm) GEN L* a* b* C15 None 10 00 0.797 36.285 −1.7 76.49 −3.18 7.82 C16 None 13 5 0 0.752 33.94 4.975.01 −3.07 7.71 C17 None 10 2 0 0.842 36.82 −3.2 75.95 −3.19 8.26 15Cyasorb 12 54 0.106 0.734 9.325 73.9 76.84 −3.51 6.67 UV 3529- H3PO3 16Cyasorb 10 56 0.1 0.77 8.465 76.3 77.04 −3.6 6.91 UV 3529- H3PO3

TABLE 6 Cyasorb UV 3529- Residual % Reduced AAGEN % H3PO4 Ti AA Residual295/5 Reduced avg Avg Ex. Amt g ppm P ppm IV dl/g ppm. AA ppm AA Gen L*avg a* b* 17 0 10 1 0.744 17.21 0.00 35.32 0.00 76.86 −1.99 18 0.02 1016 0.716 4.45 74.14 10.07 71.49 −2.22 −2.22 19 0.04 10 29 0.723 8.0753.11 9.27 73.75 76.46 −2.36 20 0.06 10 39 0.72 6.11 64.50 10.28 70.8976.76 −2.38 21 0.08 10 46 0.714 4.14 75.94 7.4 79.05 76.46 −2.41 22 0.110 61 0.687 4.32 74.90 7.61 78.45 77.31 −2.54

TABLE 7 Additive AA AAGEN AVG AVG AVG Amount Ti P IV FN 295/5 L* a* b*Example Additive (g) (ppm) (ppm) (dl/g) (ppm) (ppm) Color Color Color 23Cyasorb 0.102 10 66 0.741 3.1 7.8 77 −2.62 7.27 UV 3529- H3PO3 24Cyasorb 0.105 10 83 0.725 3.6 7.19 76.03 −2.65 8.71 UV 3529- H3PO4 25Cyasorb 0.106 10 99 0.732 3.34 7.69 76.02 −2.51 8.66 UV 3529 H3PO4

Table 6 indicates that even at the very low concentration of 0.02 weightpercent, the phosphorous acid salts of Cyasorb UV 3529 provides for adramatic lowering (>70% reduction relative to no additive) of bothresidual acetaldehyde as well as acetaldehyde generated upon melting.

Example D

To make the phosphoric acid salts of CyasorbUV 3529, two moles ofphosphoric acid are used per mole of CyasorbUV 3529, and reactedaccording to the following procedure.

To a 500-mL, round-bottomed flask equipped with a magnetic stir bar,thermocouple, and a heating mantle is added 41.18 g of Cyasorb UV-3529and 94.51 g of toluene. Cyasorb UV-3529 is a polymeric hindered aminelight stabilizer believed to conform generally to the compounds of amineformula (12) set forth above R₆=R₇=R₈=R₉=R₁₀=methyl; L₁ ishexamethylene; and (R₃)(R₄)N— collectively represent a morpholino group.The slurry is heated to 60° C. and stirred until a homogeneous solutionwas obtained. A solution of 16.23 g (0.141 mol) of phosphoric aciddissolved into 37.01 g of isopropyl alcohol is added in a small steadystream (moderate dropwise) via an addition funnel to the Cyasorb UV-3529solution with rapid stirring over approximately 100 minutes. If theaddition is too rapid, big chunks of solids form and make it difficultto stir. A slurry with light-colored solids is obtained and is stirredfor 15 min once the addition is complete. The precipitate is a mixtureof a fine white powder and sticky amber globules coated with whitepowder and is collected by suction filtration. The filter cake is washedwith seven 40 mL portions of heptane and then sucked dry on the filterpaper for 2 h. The solid is placed in a metal pan and dried over theweekend at 50° C. with a slight ingress of dry nitrogen. The dry productweighs approximately 36.48 g (66% of theory; fines in filtrate were notisolated).

A further series of polymers were prepared, employing the phosphoricacid salt of CYASORB UV 3529 (“Cyasorb UV 3529-H3PO4”). These examplesuse the melt-blending procedure outlined in Table 3 and the polymerdescribed in Example B. For Example 23, the phosphorous acid salt ofCYASORB UV 3529 is one described in Example A. Table 7 indicates thatthe levels of residual AA and AA generated upon melting were verysimilar for both the phosphoric acid salts of Cyasorb UV 3529 and thephosphorous acid salts of Cyasorb UV 3529. The average AAGen ofproduction control PET pellets tested at the same time was 22.6 ppm. Theruns with the phosphoric acid salt turned out to have a somewhat higherP level. The b* color, or yellowness, of the blends with the phosphoricacid salts may be slightly higher.

Example E

Further inventive additives were also employed: the phosphorous acidsalt of N-methylpiperidine (“NMP-H₃PO₃”), the phosphorous acid salt ofammonia (“Ammonia-H₃PO₃”), and the phosphoric acid salt ofN-methylpiperidine (“NMP-H₃PO₄”).

To make the phosphorous acid salts of N-methylpiperidine, one mole ofphosphorous acid are used per mole of N-methylpiperidine, and reactedaccording to the following procedure.

To a 500-mL, round-bottomed flask equipped with a magnetic stir bar,thermocouple, and a heating mantle is added 7.0 g of 1-methyl-piperidine(0.0704 mol) and 94.5 g of toluene. The slurry is heated to 60° C. andstirred until a homogeneous solution was obtained. A solution of 5.8 g(0.0704 mol) of phosphorous acid dissolved into 37 g of isopropylalcohol is added in a small steady stream (fast dropwise) via anaddition funnel to the 1-methyl-piperidine solution with rapid stirringover approximately 55 minutes. The reaction mixture was pumped at about5 mL/min over a period of approximately 40 minutes into a 2 L reactionvessel, fitted with a mechanical stirrer, that contained about 700 mL ofrapidly stirred heptane (476.8 g). After addition was complete, theresulting solution was stirred for about 50 minutes. Suction filtrationwas initiated and then stopped when the product was determined to be ayellow oil containing some fine white solids. The solvent was rotavappedoff using a vacuum pump and 55° C. water bath. The filter paper andflask were rinsed with heptane. The solvent was removed on a rotaryevaporator. The oil was dried over night and then for about 5 hours atabout 50° C. with a slight ingress of dry nitrogen. The product weighed7.5 g (12.75 g theory).

To make the phosphorous acid salts of ammonia, one mole of phosphorousacid are used per mole of ammonia, and reacted according to thefollowing procedure.

To a 500-mL, round-bottomed flask equipped with a magnetic stir bar,thermocouple, and a heating mantle is added 8.5 g of 28-30% ammoniumhydroxide and 94.5 g of toluene. The slurry is heated to 60° C. andstirred until a homogeneous solution was obtained. A solution of 5.8 g(0.0704 mol) of phosphorous acid dissolved into 37.1 g of isopropylalcohol is added in a small steady stream (fast dropwise) via anaddition funnel to the ammonium hydroxide solution with rapid stirringover approximately 25 minutes. The solution is stirred for 15 min oncethe addition is complete. The reaction mixture was pumped at about 5mL/min over a period of approximately 35 minutes into a 2 L reactionvessel, fitted with a mechanical stirrer that contained about 700 mL ofrapidly stirred heptane (476.8 g). After addition was complete, theresulting solution was stirred for about 60 minutes. The solvent wasrotavapped off using a vacuum pump and 55° C. water bath. Whitesemisolids were visible after all the solvent was removed. The flask wasrinsed with heptane, isopropyl alcohol & Millipore water. The solventswere removed on a rotary evaporator. The white solid is dried over nightat 50° C. with a slight ingress of dry nitrogen. The product weighed 7.3g.

To make the phosphoric acid salts of N-methylpiperidine, one mole ofphosphoric acid are used per mole of N-methylpiperidine, and reactedaccording to the following procedure.

To a 500-mL, round-bottomed flask equipped with a magnetic stir bar,thermocouple, and a heating mantle is added 7.0 g of 1-methyl-piperidineand 94.5 g of toluene. The slurry is heated to 60° C. and stirred untila homogeneous solution was obtained. A solution of 8.1 g (0.0704 mol) of85% phosphoric acid dissolved into 37 g of isopropyl alcohol is added ina small steady stream (fast dropwise) via an addition funnel to the1-methyl-piperidine solution with rapid stirring over approximately 50minutes. A yellow liquid with a white ring of solids is obtained and isstirred for 15 min once the addition is complete. After scraping stickysolids out of flask, the precipitate was collected by suctionfiltration. The filter cake is washed with eight approximately 40 mLportions of heptane and then sucked dry on the filter paper for 3 h. Thesolid is placed in a metal pan and dried over night and most of the nextday at 50° C. with a slight ingress of dry nitrogen. The product weighed12.1 g.

Per Table 8, the salts of the smaller, simpler bases had about half thereduction in AA generation of the UV 3529-H3PO3; however, the simplersalts are much less expensive.

In addition to the further inventive additives, a run was also made toinvestigate the use of an amine additive itself, and not its salt. Theresults are presented in Table 8 below. The average AAGen of productioncontrol PET pellets tested at the same time was 22.0 ppm. Cyasorb UV3529 did not reduce residual AA much; however, there was around a slightreduction in AA generation (10-15%). The amines alone are much lesseffective at lowering acetaldehyde than the amine salts made with aphosphorus-containing acid. Of the salts shown in Table 8, the ones withthe smaller, simpler organic bases had about half of the reduction in AAgeneration than that of the Cyasorb UV 3529-H3PO3 salt.

TABLE 8 Amount added % AA to XRF Residual Residual GEN % AA Ave. Ave.Ave. flask Ti XRF IhV AA AA 295/5 Gen L* a* b* Ex. Additive (g) (ppm) P(ppm) (dL/g) (ppm) Reduction (ppm) Reduction Color Color Color C18 None0 9 3 0.804 21.25 −9.8 30.54 −2.2 74.37 −1.93 7.33 C19 None 0 10 5 0.7917.45 9.8 29.25 2.2 76.12 −2.22 8.03 C20 Cyasorb 0.099 10 1 0.817 17.439.9 25.71 14 74.78 1.88 8.43 3529 26 Cyasorb 0.101 10 57 0.747 4.57 76.411.96 60 76.73 −2.73 7.82 UV 3529- H3PO3 27 Cyasorb 0.103 10 59 0.7573.53 81.8 12.4 58.5 73.77 −2.65 7.32 UV 3529- H3PO3 28 NMP- 0.048 10 660.768 7.18 62.9 20.73 30.7 76.2 −2.72 7.63 H3PO3 29 NMP- 0.052 9 850.754 13.87 28.3 18.88 36.8 75.01 −2.64 7.52 H3PO3 30 NMP- 0.053 10 780.746 13.94 28 20.35 31.9 69.76 −2.35 8.7 H3PO4 31 Ammonia- 0.028 10 630.754 6.78 65 19.33 35.3 73.81 −2.58 8.73 H3PO3

While the amine portion of the salt may scavenge some AA as shown inExample C20 in Table 8, without being bound to a theory, it is thoughtthat the predominant mechanism is thought to be catalyst deactivation.

Example F

Choosing an amino acid as the organic base offers the possibility thatthe carboxylic acid group of the amino acid may react into the PETchain.

To make the phosphoric acid salts of L-histidine, two moles ofphosphoric acid are used per mole of L-histidine, and reacted accordingto the following procedure.

To a 500-mL, round-bottomed flask equipped with a magnetic stir bar,thermocouple, and a heating mantle is added 10.94 g of L-histidine and143.97 g of Millipore water. The slurry is heated to 60° C. and stirreduntil a homogeneous solution was obtained. A solution of 16.397 g ofphosphoric acid dissolved into 37 g of Millipore water is added in asmall steady stream (fast dropwise) via an addition funnel to theL-histidine solution with rapid stirring over approximately 35 minutes.The solution is stirred for about 35 min once the addition is complete.The clear solution was transferred to a single-necked, 500 mLround-bottomed flask. The aqueous solvent was removed by freeze drying.The liquid was frozen while manually rotating in a dry ice/acetone bath.A lyophilizer was used for 3 days, 4 hours and 17 min. The white solidweighed 24.829 g (theory 24.722 g). By XRF, wt./wt. % P in the whitesolid was 17.17% (theory 17.6%).

To make the phosphoric acid salts of L-alanine, one mole of phosphoricacid are used per mole of L-alanine, and reacted according to thefollowing procedure.

To a 500-mL, round-bottomed flask equipped with a magnetic stir bar,thermocouple, and a heating mantle is added 6.275 g of L-alanine and94.5 g of Millipore water. The slurry is heated to 60° C. and stirreduntil a homogeneous solution was obtained. A solution of 8.201 g ofphosphoric acid dissolved into 37.01 g of Millipore water is added in asmall steady stream (fast dropwise) via an addition funnel to theL-alanine solution with rapid stirring over approximately 17 minutes.The solution is stirred for at least 15 min once the addition iscomplete. The clear solution was transferred to a single-necked, 500 mLround-bottomed flask. The aqueous solvent was removed by freeze drying.The liquid was frozen while manually rotating in a dry ice/acetone bath.A lyophilizer was used for 1 days, 19 hours and 15 min. The clear,viscous oil weighed 14.808 g (theory 13.17 g). By XRF, wt./wt. % P inthe clear oil was 11.92% (theory 16.6%).

A further series of polymers were prepared, employing the phosphoricacid salt of L-histidine, phosphoric acid salt of L-alanine, bothdescribed above in this example, and the phosphoric acid salt of CYASORBUV 3529 (“Cyasorb UV 3529-H3PO4”) described in Example D. These examplesuse the melt-blending procedure outlined in Table 3 and the polymerdescribed in Example B.

Table 9 indicates the two amino acid salts of phosphoric acid reduceresidual AA by 79-83% and AA generation upon melting by 65-66%. TheCYASORB UV 3529 salt of phosphoric acid reduces residual AA by about87%, AA generation upon melting by about 75%, and has the best color.While the % reduction in AA generation is about 10% less for the aminoacid salts than for the Cyasorb UV 3529 salt, the amino acids are lessexpensive, copolymerizable (less extractability), and water soluble (noVOC during salt preparation). The color and clarity are better forExample 34 with the L-alanine salt than for Example 33 with theL-histidine salt. L-alanine is also more water soluble than L-histidine,which requires more dilute conditions to get it into aqueous solution.The phosphoric acid salt of L-alanine is an oil, which may make it moreeconomical to add than a solid salt like the phosphoric acid salt ofL-histidine.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

TABLE 9 Amount % AA added XRF XRF Residual Residual GEN % AA Ave. Ave.Ave. to Ti P IhV AA AA 295/5 Gen L* a* b* Ex. Additive flask (g) (ppm)(ppm) (dL/g) (ppm) Reduction (ppm) Reduction Color Color Color C21 None0 9 2 0.781 11.5 0 28.7 0 75.9 −2.1 8.2 32 Cyasorb **** 9 90 0.745 1.586.8 7.2 74.8 76.5 −2.3 8.0 UV 3529- H3PO4 33 Histidine- **** 10 630.756 1.9 83.2 10.0 65.1 74.0 −2.0 10.7 H3PO4 34 Alanine- **** 10 640.736 2.5 78.7 9.7 66.1 75.1 −2.0 9.0 H3PO4

1. A method comprising (i) introducing into a melt processing zone astream comprising a an amine salt of one or more of phosphorous acid andphosphoric acid and a stream comprising solid polyester particles havinga residual acetaldehyde level of 10 ppm or less, and melting theparticles to form a molten polyester polymer composition; and (ii)forming a bottle preform from the molten polymer composition.
 2. Themethod of claim 1, wherein the bottle preform has a residualacetaldehyde content of 10 ppm or less.
 3. The method of claim 1,wherein the bottle preform has a residual acetaldehyde content of 8 ppmor less.
 4. A method comprising (i) introducing into a melt processingzone a stream of polyester particles containing a randomly dispersedamine salt of one or more of phosphorous acid and phosphoric acid, and astream comprising solid polyester particles having a residualacetaldehyde level of 10 ppm or less, and melting the particles to forma molten polyester polymer composition; and (ii) forming a bottlepreform from the molten polymer composition.
 5. The method of claim 4,wherein the bottle preform has a residual acetaldehyde content of 10 ppmor less.
 6. The method of claim 4, wherein the bottle preform has aresidual acetaldehyde content of 8 ppm or less.